Ultrahigh-grade non-oriented silicon steel cold rolling method

Abstract

The invention relates to a cold rolling method for non-oriented silicon steel, in particular to a cold rolling method for ultra-high-grade non-oriented silicon steel. The cold rolling method comprises the following steps: step 1, a first rolling process: a first cold rolling production method for a steel coil; and 2, a second rolling process: carrying out a second cold rolling production method on the steel coil subjected to the first annealing. The small reduction rate of 26-30% is adopted for the first pass of the first rolling process, meanwhile, the control standard of micro edge waves is adopted for the edge, and the purpose is to reduce or avoid the edge crack defect.

Description

Technical Field

[0001] The invention relates to a cold rolling method for non-oriented silicon steel, in particular to a two-rolling-pass ultra-high grade cold rolling method for non-oriented silicon steel. Background Art

[0002] With the rapid development of the electrical industry, the demand for magnetic properties and mechanical properties of electromagnetic materials is getting higher and higher. However, with the increase of silicon content, the brittleness of the strip increases, and the difficulty of processing increases exponentially. In order to further improve the magnetic induction intensity of silicon steel sheets, ultra-high grade non-oriented silicon steel (silicon content between 3.0-3.5%) is achieved by two annealing processes during rolling. Compared with the process of ordinary high-grade cold-rolled silicon steel, its characteristics are that the strip is rolled to the intermediate thickness for the first time in a single-stand rolling mill after heat treatment in the normalizing unit, and then rolled to the final thickness for the second time in a single-stand rolling mill after the first annealing in the continuous annealing unit, and then annealed and coated in the continuous annealing unit for the second time. This production method has one more intermediate annealing and one more cold rolling than the normal process. The final thickness of the product is generally between 0.15-0.35mm, and the thickness of the first rolling process is controlled between 0.4-0.7mm according to the process design. The thickness of the billet is between 2.1-2.3mm. The process described in the present invention is in the cold rolling process.

[0003] The cold rolling described in the present invention is produced by a twenty-high rolling mill, specifically a split 21-type twenty-high rolling mill, and the use range of the working roll diameter is 65-100mm.

[0004] The process technology route for improving magnetic properties is to adopt two cold rolling and two annealing. The difficulty of this process is that the surface of the strip steel is oxidized in the annealing furnace after the first annealing. During the second rolling, the rolling pressure fluctuates greatly, the rolling is extremely difficult, the strip breaks frequently, the production efficiency is low, and the yield rate is low. After the second rolling process, there is a serious color difference on the surface, the plate shape is unstable, and the quality qualified product rate is low.

[0005] The present invention starts from the mechanism of surface oxidation of the strip steel after the first annealing, improves the cold rolling process, reduces the degree of surface oxidation of the strip steel, and improves the surface quality; reduces the generation of crack defects, solves the problem of strip breakage due to cracks in the second rolling process; optimizes the second rolling process, solves the influence of surface oxidation of the strip steel after the first annealing on cold rolling, and finally improves the rolling efficiency, yield rate and surface quality of the strip steel. Summary of the invention

[0006] The purpose of the present invention is to provide a method for cold rolling ultra-high grade non-oriented silicon steel in view of the above problems.

[0007] The object of the present invention is achieved as follows: A method for cold rolling ultra-high grade non-oriented silicon steel, comprising the following steps: Step 1: First rolling process: The first cold rolling production method of the steel coil: (1) The billet thickness is 2.1-2.3 mm, the thickness of the first rolling process is between 0.4-0.7 mm, and the total number of rolling passes in the first rolling process is 4; (2) The first pass reduction rate of the first rolling process is controlled between 26-32%, the front tension is 7-10 kg / mm², and the rear tension is between 2.5-3.5 kg / mm²; (3) The middle pass reduction rate of the first rolling process is controlled between 30-38%, the front tension is 8-15 kg / mm², and the rear tension is between 4-12 kg / mm²; (4) The last pass reduction rate of the first rolling process is controlled between 25-33%, the front tension is 18-22 kg / mm², and the rear tension is between 9-15 kg / mm²; (5) The process lubricating medium used in the above rolling is an emulsion; (6) After the first cold rolling, the first annealing is carried out, the annealing process speed is 80-150m / min, and the process temperature is 900-1000℃; Step 2: Second rolling process: The steel coil after the first annealing is subjected to the second cold rolling production method: (1) The second rolling process adopts 2-3 passes of rolling, and the target thickness is 0.15mm-0.3mm; (2) The first pass reduction rate of the second rolling process is controlled between 28-40%, the front tension is 18-22kg / mm², and the rear tension is (3) The second pass reduction rate of the second rolling process is controlled between 28-40%, the front tension is 20-25kg / mm², and the rear tension is between 13-18kg / mm²; (4) The last pass reduction rate of the second rolling process is controlled between 29-33%, the front tension is 22-25kg / mm², and the rear tension is between 13-18kg / mm²; (5) The process lubricating medium used in the above rolling is emulsion.

[0008] In the first cold rolling production method of the steel coil in step one, the working roll roughness of the first pass to the third to last pass adopts a large roughness working roll of 1.2-2.0μm; the roller diameter range of the working roll in the first pass is 70-100mm; the working roll roughness of the last two passes adopts a small roughness working roll of 0.15-0.4μm; the roller diameter range of the last two passes is 70-100mm; the leader strip is cut off before the last production pass and the steel sleeve is installed; the rolling speed of the first pass is 80-260m / min, the rolling speed of the second pass is 200-400m / min, and the rolling speed of other passes is 400-800m / min; the first pass is controlled by micro-edge wave, that is, the plate shape meter shows the wave shape is 10-20I, and the other passes are controlled by small edge wave, that is, the plate shape meter shows the wave shape is 25-35I.

[0009] If the second rolling process in the second cold rolling production method of step 2 consists of two rolling passes, step (3) in the production method of the second rolling process is omitted, and step (2) directly jumps to (4); the working roll roughness of the first pass uses a working roll of 0.6-1.0 μm; the working roll roughness of the last pass uses a working roll of 0.15-0.4 μm; the absolute reduction of all passes in the second rolling process is 0.05-0.3 mm, and the rolling speed of each pass is between 200-600 m / min; before the last rolling pass, a steel sleeve is placed on the coiler; during the first rolling pass, the speed increase process adopts an intermittent method, that is, speed increase-maintain-speed increase-maintain... step by step, and the speed is maintained every 30-80 m.

[0010] The emulsion temperature of the first rolling process is 45-60°C and the emulsion concentration is 3-5%.

[0011] The emulsion temperature of the second rolling process is 45-60°C and the emulsion concentration is 6-8%.

[0012] The beneficial effects of the present invention are: 1. The first pass of the first rolling process described in the present invention adopts a small reduction rate of 26-30%, and the edge adopts a micro-edge wave control standard, the purpose of which is to reduce or avoid the occurrence of edge crack defects.

[0013] 2. In the present invention, all rolling passes before the last pass of the first rolling process use working rolls with large roughness, which is beneficial to reducing rolling cracks on the one hand, and on the other hand, is to achieve high-speed and stable rolling under low tension.

[0014] 3. In the first rolling process of the present invention, except for the first pass, the plate shape control adopts small edge wave control, the purpose of which is to reduce the stress on the edge of the strip and prevent the occurrence or extension of cracks.

[0015] 4. The present invention adopts a small roughness working roll at the last pass of the first rolling process, the purpose of which is to reduce the microscopic surface area of ​​the strip surface and the contact area between the strip surface and the atmosphere in the furnace, thereby reducing the oxidation degree of the strip.

[0016] 5. The first pass of the second rolling process of the present invention uses a working roll with a larger roughness, the purpose of which is to break the oxide layer on the surface of the strip, reduce the fluctuation of the rolling pressure during the rolling process, improve the surface uniformity and rolling stability, and avoid color difference on the surface of the strip.

[0017] 6. The present invention adopts a small roughness working roll in the last pass of the second rolling process, the purpose of which is to ensure the final surface roughness of the strip while improving the surface consistency. DETAILED DESCRIPTION

[0018] The rapid development of electric vehicles and other related industries has placed higher and higher requirements on the electromagnetic and mechanical properties of silicon steel. With the upgrading of silicon steel process equipment, the process flow of cold-rolled silicon steel has undergone major changes. For example, thin-gauge high-grade and ultra-high-grade non-oriented silicon steel has been mass-produced in cold rolling units. However, varieties with high requirements for electromagnetic and mechanical properties can only be achieved through a production process of two intermediate annealings and two rolling passes. The downstream market has an increasing demand for high-performance products, but due to the high difficulty of rolling, production costs remain high. The present invention improves production efficiency and product quality from the perspective of innovative design of the cold rolling process, greatly reduces production costs, and enhances market competitiveness.

[0019] The present invention mainly solves the above problems from the aspects of rolling design, optimization of the roll system and process medium parameters, etc. The specific process design and production plan are as follows.

[0020] Description of the production process before the first cold rolling: Normalization process: The hot-rolled material undergoes heat treatment, pickling and trimming by the CP unit.

[0021] Preparation unit: After normalization, the steel coil is sent to the preparation unit for heating and welding of the lead strip.

[0022] The above two processes are the conventional production processes for producing ultra-high grade non-oriented silicon steel at present, and the present invention will not explain them in detail. The scope of the present invention is the cold rolling process, which is described in detail as follows.

[0023] 1. Production method of the first cold rolling of steel coil after normalized pickling: Process design method and steps: (1) The thickness of the billet is 2.1-2.3 mm, the thickness of the first rolling process is between 0.4-0.7 mm, and the total number of rolling passes in the first rolling process is generally 4.

[0024] (2) The first pass reduction rate of the first rolling process is controlled between 26-32%. The front tension is 7-10kg / mm², and the rear tension is between 2.5-3.5kg / mm². Preferably, the front tension is 7.8kg / mm² and the rear tension is 2.7 kg / mm².

[0025] (3) The reduction rate of the middle pass in the first rolling process is controlled between 30-38%. The front tension is 8-15kg / mm², and the rear tension is between 4-12kg / mm².

[0026] (4) The reduction rate of the last pass of the first rolling process is controlled between 25-33%. The front tension is 18-22kg / mm², and the rear tension is between 9-15kg / mm².

[0027] Further explanation: (1) The working rolls from the first pass to the third to last pass have a roughness of 1.2-2.0 μm, preferably 1.5 μm.

[0028] (2) The diameter of the working roll in the first pass is in the range of 70-100 mm, and preferably a working roll of 95-100 mm is used.

[0029] (3) The working rolls in the last two passes have a roughness of 0.15-0.4 μm, preferably 0.2 μm.

[0030] (4) The diameter of the working rolls in the last two passes is in the range of 70-100 mm, preferably 70-80 mm in diameter.

[0031] (5) Before the last production, the guide belt is removed and the steel sleeve is installed.

[0032] (6) The rolling speed of each of the above passes is determined according to the design capacity of the unit. Theoretically, the design speed of the unit can be reached and there is no limitation in the process.

[0033] (7) The first pass is controlled by micro-edge waves, wherein the micro-edge waves are waves with a shape of 10-20I as displayed by the board shape meter.

[0034] (8) The other passes mentioned above are controlled by small side waves, and the small side waves mentioned are waves with a shape meter showing a shape of 25-35I.

[0035] 2. Production method of the second rolling process (after the first annealing): process design method and steps: (1) According to the overall process design, the second rolling process generally adopts 2-3 rolling passes.

[0036] (2) The first pass reduction rate of the second rolling process is controlled between 28-40%. The front tension is 18-22kg / mm², and the rear tension is between 12-17kg / mm². Preferably, the front tension is 20kg / mm² and the rear tension is 13kg / mm².

[0037] (3) The second pass reduction rate of the second rolling process is controlled between 28-40%. The front tension is 20-25kg / mm², and the rear tension is between 13-18kg / mm². Preferably, the front tension is 20.5kg / mm² and the rear tension is 14kg / mm².

[0038] (4) The reduction rate of the last pass of the second rolling process is controlled between 29-33%. The front tension is 22-25kg / mm², and the rear tension is between 13-18kg / mm². Preferably, the front tension is 23.5kg / mm² and the rear tension is 16.5kg / mm².

[0039] Further explanation: (1) If the second rolling process consists of two rolling passes, step (3) in the production method of the second rolling process (after the first annealing) is omitted, and step (2) directly jumps to (4).

[0040] (2) The roughness of the working roll in the first pass is 0.6-1.0 μm, preferably 0.75 μm.

[0041] (3) The working roll roughness of the last pass is 0.15-0.4 μm, preferably 0.2 μm.

[0042] (4) The absolute reduction in the above passes is greater than 0.05 mm.

[0043] (5) Before the last rolling, a steel sleeve is placed on the coiler to prevent coil collapse and coiler folding.

[0044] (6) During the first rolling process, the speed is increased intermittently (increase speed-maintain-increase speed-maintain...), and preferably, the speed is maintained every time the speed increases by 30m.

[0045] 3. The process medium parameters of the two rolling processes are shown in the following table.

[0046]

[0047] This case is applied to the twenty-high rolling mill of the silicon steel division of Baowu Taigang Stainless Steel Co., Ltd. The specific embodiment is described as follows. Embodiment 1

[0048] For example, the steel type is ultra-high grade non-oriented silicon steel, with a silicon content of 3.33%, a width of 1130mm, a strip thickness of 2.25mm after normalization and pickling, a first rolling thickness of 0.5mm, and a second rolling thickness of 0.245mm. The specific rolling conditions are as follows: 1. After the strip is normalized and trimmed by the CP unit, it is heated to 120℃ in the preparation unit and welded to the leader.

[0049] 2. Specific cold rolling steps and parameters: First rolling process: (1) Replace the working roll before rolling, preferably with a roughness of 1.5 μm and a roll diameter of 85-100 mm.

[0050] (2) Replace the working roll and install the sleeve before the finished product. The working roll roughness is preferably 0.2μm and the roll diameter is 70-85mm.

[0051] (3) The rolling procedure is as shown in the following table.

[0052]

[0053] Second rolling process: The billet is the material that has undergone the first annealing.

[0054] (1) Replace the working rolls before rolling, preferably with a roughness of 0.75 μm and a roll diameter of 70-85 mm.

[0055] (2) Replace the working roll in the previous pass of the finished product and sleeve it on the coiler. The working roll roughness is preferably 0.2μm and the roll diameter is 70-85mm.

[0056] (3) The rolling procedure is as shown in the following table.

[0057] Embodiment 2

[0058] The steel type is ultra-high grade non-oriented silicon steel, with a silicon content of 3.28%, a width of 1190mm, a strip thickness of 2.2mm after normalization and pickling, a first rolling thickness of 0.47mm, and a second rolling thickness of 0.15mm. The specific rolling conditions are as follows: 1. After normalization and trimming of the strip by the CP unit, it is heated to 120℃ in the preparation unit and welded to the leader.

[0059] 2. Specific cold rolling steps and parameters: First rolling process: (1) Replace the working roll before rolling, preferably with a roughness of 1.5 μm and a roll diameter of 85-100 mm.

[0060] (2) Replace the working roll and install the sleeve before the finished product. The working roll roughness is preferably 0.2μm and the roll diameter is 70-85mm.

[0061] (3) The rolling procedure is as shown in the following table.

[0062]

[0063] Second rolling process: The billet is the material that has undergone the first annealing.

[0064] (1) Replace the working rolls before rolling, preferably with a roughness of 0.75 μm and a roll diameter of 75-85 mm.

[0065] (2) Replace the working roll and install the sleeve before the finished product. The working roll roughness is preferably 0.2μm and the roll diameter is 75-85mm.

[0066] (3) The rolling procedure is as shown in the following table.

[0067]

[0068] Note: Since the concentration of the emulsion is adjusted by the ratio of oil and water on site, it is impossible to achieve a specific quantitative value and can only be controlled within a certain range.

[0069] Effect comparison between the embodiments of the present invention and the comparative examples: 1. For example, the silicon content of ultra-high grade non-oriented silicon steel is 3.3±0.05%, and the width is 1050-1200mm. The hot-rolled thickness of the billet is 2.1-2.3mm, the thickness of the first rolling process is 0.5mm, and the thickness of the second rolling process is 0.245mm. The comparison is shown in the following table.

[0070]

[0071] This implementation is only the best example and is not a restrictive implementation of the technical solution of the present invention.

[0072] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for cold rolling ultra-high grade non-oriented silicon steel, characterized in that: The following steps are involved: Step 1: First rolling process: First cold rolling of steel coil Production method: (1) The billet thickness is 2.1-2.3 mm, the thickness of the first rolling process is between 0.4-0.7 mm, and the total number of rolling passes in the first rolling process is 4; (2) The first pass reduction rate of the first rolling process is controlled between 26-32%, the front tension is 7-10kg / mm², and the rear tension is between 2.5-3.5kg / mm²; (3) The reduction rate of the middle pass in the first rolling process is controlled between 30-38%, the front tension is 8-15kg / mm², and the rear tension is between 4-12kg / mm²; (4) The reduction rate of the last pass of the first rolling process is controlled between 25-33%, the front tension is 18-22kg / mm², and the rear tension is between 9-15kg / mm²; (5) The lubricating medium used in the above rolling process is emulsion; (6) After the first cold rolling, the first annealing is carried out, the annealing process speed is 80-150m / min, and the process temperature is 900-1000℃; Step 2: Second rolling process: The steel coil after the first annealing is subjected to a second cold rolling process. Production method: (1) The second rolling process uses 2-3 passes, with a target thickness of 0.15mm-0.3mm; (2) The first pass reduction rate of the second rolling process is controlled between 28-40%, the front tension is 18-22kg / mm², and the rear tension is between 12-17kg / mm²; (3) The second pass reduction rate of the second rolling process is controlled between 28-40%, the front tension is 20-25kg / mm², and the rear tension is between 13-18kg / mm²; (4) The reduction rate of the last pass of the second rolling process is controlled between 29-33%, the front tension is 22-25kg / mm², and the rear tension is between 13-18kg / mm²; (5) The lubricating medium used in the above rolling process is emulsion.

2. The method for cold rolling ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: In the first cold rolling production method of the steel coil in step one, the working roll roughness of the first pass to the third to last pass adopts a large roughness working roll of 1.2-2.0μm; the roller diameter range of the working roll in the first pass is 70-100mm; the working roll roughness of the last two passes adopts a small roughness working roll of 0.15-0.4μm; the roller diameter range of the last two passes is 70-100mm; the leader strip is cut off before the last production pass and the steel sleeve is installed; the rolling speed of the first pass is 80-260m / min, the rolling speed of the second pass is 200-400m / min, and the rolling speed of other passes is 400-800m / min; the first pass is controlled by micro-edge wave, that is, the plate shape meter shows the wave shape is 10-20I, and the other passes are controlled by small edge wave, that is, the plate shape meter shows the wave shape is 25-35I.

3. The method for cold rolling ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: If the second rolling process in the second cold rolling production method of step 2 consists of two rolling passes, step (3) in the production method of the second rolling process is omitted, and step (2) directly jumps to (4); The working roll roughness of the first pass is 0.6-1.0μm; the working roll roughness of the last pass is 0.15-0.4μm; the absolute reduction of all passes in the second rolling process is 0.05-0.3mm, and the rolling speed of each pass is between 200-600m / min; the steel sleeve is put on the coiler before the last rolling pass; during the first rolling pass, the speed increase process adopts an intermittent method, that is, speed up-maintain-speed up-maintain... step by step, and the speed is maintained every 30-80m.

4. The method for cold rolling ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: The emulsion temperature of the first rolling process is 45-60°C and the emulsion concentration is 3-5%.

5. The method for cold rolling ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: The emulsion temperature of the second rolling process is 45-60°C and the emulsion concentration is 6-8%.

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